Engine piston



Sept 4,1923.

J. THOMSON ENGINE PISTON Filed April 17 1922 INVENTOR;

Patented Sept. 4, 1923.

JOHN THOMSON, OF BROOKI LYN, NEW YORK.

ENGINE Application fi led April 17,

To all whom it may concern:

Be it known that I, JoHN THOMSON, a citizen of the United States, and a resident of the borough of Brooklyn, city and State of New York, have invented an Engine Piston, of which the following is a specification.

Divested of various co-ordinating features, which, however, will be hereinafter to pointed out, the essence of this invention consists in forming a single acting engme piston by mounting thereon a plurality of packing-rings each of which is formed from two or more distinct circular segments, com- E5 posed of monolithiccarbon-graphite; and the objects thereof are to provide a piston which shall remain well nigh interminably ti ht in its cylinder; whose co-eflicient of frlction shall be a minimum and whose proat ductive and up-keep cost, both as to material and construction, shall be substantially less than the prevailing types now in use.

In the drawings, which constitute a partof this specification,

Figure 1 is a vertical, center section of the piston, taken transversely of the connecting rod pin;

Figure 2 is a composite view, half in elevation and half in vertical, center section,

so taken longitudinally of the connecting rod Fi re 3 is an interior plan view, projecte from Figure 1;

Figure 4 is an outer plan view of the head, revolved from Figure 2;

Fi re 5 is a detached side view of a packing ring, shown as being formed in three segmental circular parts; and

Figure 6 is an edge view of said ring,

6 0 pro'ected from Figure 5.

he drawings are approximately full scale representations, utilizable in practice for the smaller sizes of gas engines in 1110- tor driven vehicles, and the principal references, by letters or numerals, are uniformly inaintained throughout the several illustra- IOIIS.

The head, A, the cylindrical portion, B, and the hubs, C, 0 in which the connect 60 mg rod, D, and-its pin, 7, are mounted,

constitute the piston assembla e. The piston, per se, would ordinarily e cast from metal. The reciprocal swing of the connectlng rod, shown in dotted outline, is

denoted by the center lines a, b, Figure 1.

is desirable, if not in fact essential, for

HsroN. 1922. Serial No. 554,099.

The broken section, E, Figure 2, denotes the en ine clinder.

especting the established type of split piston-ring, it is deemed sufiicient to here briefly state that they are necessarily formed of a metal which will stand being considerably spread, whereby to pass over the outer diameter of the piston and then snap into its recess; also, if snugly fitted in said recess, which is desirable in practice, oil may thus not reach its side-surfaces, when it is liable to freeze and cease to function properly. Moreover, as the extent of deformation is relatively considerable, that is in order to pass them over the outer diameter ofa plston, their thickness is restricted and the area of side-bearing surface, in view of the duty to be performed, is less than would otherwise be acceptable.

In the present instance, the packing rings, H, which may be formed to any desired wall-thickness, are'separated in two or more circular segments, as 8, 9, 10, the several co-ordinating segments constitutin a true circle, and are then placed, piecey-piece, into their respective grooves, as 12, 13, of the piston.

These rings, formed of co-ordinating circular segments, could be produced by machining each segment separately; but the cost thereof would be excemive, as it would be well-nigh practically impossible to thus produce them, in a regular routine operation, with such an average degree of accuracy as proper performance. However, this dlfliculty iswholly obviated bly means-of the following maneuvre: First y, the rings are prlmarily produced as integral rings, being thus readily and inexpensively machinable to recise dimensions, as from rods or tubes; and secondly, each ring is thenafter separated into as many segments as may be desired by rupturing it apart. If the fractures are effected quickly, the cleavages, as 14, Wlll be radial, clean and sharp; and they will again go together with such exactness that their junctures are barely perceptible. An effective way of rupturing the rings is denoted by the broken lines of Figure 5, that 5 is by means of a mandrel, 16, having three sharp edged blades, as 17 which may somewhat tapered lengthwise so as to pr marily nick the rings. It lends to the umformity of the result if the ring itself is held in a yielding tube, such as rubber, which prevents the ruptured segments from unduly flying out. This mode of separating a body, that is by breaking it, whereby it may again be placed together with the utmost accuracy at the juncture, has been successfully practiced in the case of certain hardened steel dies, whereby the joint-line was substantially more perfect than could'be attained by the most refinedmachining or manual fitting. 7

As stated at the outset hereof, these segmental rings are formed of monolithic carhon-graphite, this term being used in a general, inclusive sense; for example, as relates to amorphous carbon which has been partially or wholly graphitized, as by the electric process of Acheson; or carbongraphite, as powder, which has been suitably monolithically die-molded; or to mono lithic carbon-graphite which has been more or less metallized. Among the dominant characteristics of carbon-graphite, the following may be mentioned, in that they are pertinent to the present case: It is dense, yet porous; highly resilient; does not side-flow, under pressure; machines readily, to precise dimensions; withstands oxidization, at rela tively high temperatures; its coeflicient of friction, especially, when it acts upon itself, is second only to that of oil; and its endurance against abrasive action is phenomlnal.

The peculiarly excellent feature of separating the rings by cleavage presents a certain detail objection in manufacturin in that, to realize the desired result, each se of segments must be kept separate from any other set; also if or when finishing their outer peripheral faces, or when placed in the piston, or when the latter is shipped or handled, should two rings become displaced it might be less expensive to scrap them than to attempt their correct re-assemblage. But this difficulty can be readily obviated by lightly, or for that matter effectively,

7 cementing each pair of co-ordinating fractures together; which can be well and conveniently effected by brushing thereon a d1- luted solution of sodium-silicate. If simply air-set, the joints can be thenafter separated; if heated, especially if a modicum of high grade clay is added, the joints themselves may be made as resistant to fracture as other portions of the ring.

As denoted in the drawings, the area of side-bearing surfaces of the rings in their grooves is very liberal for the duty required,

and can readily be increased if desired. This feature, taken in conjunction with the separability of the segments, makes it feasible to machine the upper recess, 12 deeper than that of the lower recesses, thereby forming an annular space, J, with which is connected one or more drilled ports, as18, 19,

memes this ring is proportionate to the variablegas-pressure upon the piston-head; and, as each segment is a free member, the distribution of said thrust is evenly distributed and uniformly resisted.

In primarily applying. the piston to the engine-cylinder it should fit quite snugly. In this Wise, when first put into action, carbon-gra hite will be ru tured from the faces of the rings; be trans erred to the contacting surface and be then rubbed and burnished to place, forming thereon a plating,

or skin, composed of molecular-like particles.

Bearing in mind that no amount of pressure will cause carbon-graphite to freeze, either upon itself or a metal upon it, the fact should at once be perceived that the side-fits of the carbon-graphite rings in their grooves, and their physical contact upon the wall of the engine-cylinder, can be much closer at the outset, and distinctly more intense, than would be feasible in the case of metal rings; for, whilst the friction primarily developed, due to the intensity of impingement, will be greater than is necessary this will progressively decrease until the resistance to movement becomes a minimum.

The element. of thermal expansion and contraction in the piston and its rings also plays an important part; but, as this has been elsewhere dealt with, it needs not be here repeated.

It is to be observed that, as the piston is whollyguided by the carbon-graphite rings, its outer diameter may be so reduced as to produce very effective baffle-grooves between the rings, as 20, 21, Figure 2.

A preferred mode of construction, which is satisfactorily effective and the less expensive, is to form the upper ring, or rings, of metallized carbon-graphite and the lower ring, or rings, of the softer, fully graphitized carbon.

Obviously, if for any reason required, these segmental rings of monolithic carhon-graphite can be readily removed and substituted.

In motor-driven vehicles, actuated by gas engines, the paramount advantage, at the present time, of an engine-piston which will start tight and stay .tight does not reside,

as hitherto, in holding the gas pressure to a maximum but pertains to preventing lubricating oil from reaching the explosion chamber wherein it is oxidized, forming hydro-carbon depositions, to the detriment of the piston, the engine-cylinder and the controlling valves. In a practical sense, as has been demonstrated, the foregoing objections are largely, if not wholly, avoidable when the system here presented is availed of. I

What I claim is:

An engine-piston provided with monolithic carbon-graphite packing rings formed of inserted circular segments ruptured from integral rings and re-set in the piston ringgrooves in the order of their original cleavages.

This specification signed this 8th day of December, A. D, 1921.

JOHN THOMSON. 

